This invention relates to apparatus for releasable connection to a member embedded in an object adjacent to a cavity which provides access to the member and communicates with an opening in an external surface of the object, and to a combination of the apparatus and member.
In the past, various types of apparatus have been employed in combination with members which are embedded in objects and to which the apparatus may be connected for the purpose of lifting the objects, such as by lifting or hoisting mechanism attached to the apparatus. After a lifting operation, the apparatus is disconnected from the member, which remains embedded in the object.
A specific combination embodies a pickup unit and an anchor insert, the latter being embedded in a concrete body and the former being releasably or detachably connected thereto for the purpose of lifting the body. U.S. Pat. Nos. 3,431,012 to Courtois et al. and 4,018,470 to Tye, among others, disclose such pickup units and inserts, and the structures disclosed have been in extensive commercial use, where they have been employed safely and effectively in the tilt-up erection of large and heavy concrete slabs which are incorporated into building structures as wall panels. The anchor inserts employed in the foregoing combinations have been constructed employing anchor rods or anchor rod sections as the parts of the inserts serving to transfer the weight loads of the concrete slabs to the pickup units, which in turn transfer the loads to lifting apparatus. The pickup units of the patents employ a locking stem having a T-head at its inner end. The stem of a pickup unit is engaged with or connected to the spaced anchor rods of an insert by inserting the T-head between them, and rotating the stem through an angle of 90.degree., to place lifting surfaces on the T-head beneath thrust surfaces on the anchor rods for interengaging the two. Following a lifting operation, the locking stem is rotated 90.degree., to release the stem from engagement with the anchor rods, after which the entire pickup unit may be removed from the slab.
Recently, pickup units having stem-like housings in which laterally slidable lifting lugs are mounted, have been employed with inserts embedded in concrete slabs and engaged by the lugs for lifting the slabs. The lugs are moved laterally into and out of engagement with the inserts by operation of an actuator movable longitudinally in the housing. An advantage of the structures is that the pickup units may be removed from erected slabs merely by exerting an outward pull on the actuators, to move them longitudinally, and the pull may be exerted by an operator at a remote point on the ground, acting through the medium of a lanyard or a lever. Such pickup units and anchor inserts are disclosed in my U.S. Pat. No. 4,123,882 with James E. Case and Richard L. Ruppert, and in U.S. Pat. No. 4,017,115.
A pickup unit having lifting lugs which rotate reciprocally between engagement and disengagement positions with respect to a conical insert in a concrete body is disclosed in U.S. Pat. No. 4,068,879. The lugs are supported by pivot pins, which, therefore, must bear the entire weight load as it is transferred to the lifting mechanism, placing the pins under high shear stress. Apparatus embodying a pickup unit having rotatable lugs for lifting containers or vessels is disclosed in U.S. Pat. No. 3,284,125. In this structure, a pivot pin is relied upon to resist the torque to which the lugs are subjected by the weight of the load acting at the extremities of the lugs, thereby placing the pin under shear stress. A releasable fastening means employing rotatable load-engaging lugs which, similarly, place pivot pins under shear stress is disclosed in U.S. Pat. No. 3,534,650.